1. Field of the Invention:
The present invention relates to a process for preparing an asphalt composition.
2. Description of the Prior Art:
A cationic asphalt emulsion has been widely used for asphalt pavement or road repair. The cationic asphalt which can be easily applied is highly adhesive to aggregates because of the cationic nature of the asphalt and it has a high demulsifying velocity which advantageously permits rapid reopening of the paved area to traffic. However, the physical properties of conventional cationic asphalt emulsions are not satisfactory.
Accordingly, various efforts for improving the physical properties without sacrificing the advantages of the asphalt emulsion, especially by improving the physical properties by adding a latex which also lengthens the life of the paved road and decreases road repair, have been undertaken. However, most conventional latexes are anionic or nonionic or contain anionic or nonionic surfactants. The cationic asphalt emulsion will combine with an anionic latex only with difficulty. Although a nonionic emulsified latex can be combined with a cationic asphalt emulsion, the high demulsifying property of the cationic asphalt emulsion will be disadvantageously decreased, and the surfactant will remain in the asphalt after demulsification, whereby the physical properties will disadvantageously be affected and satisfactory results will not be obtained.
The preparation of a cationic latex by emulsion-polymerization in the presence of a cationic emulsifier while preventing coagulation by adding a nonionic or amphoteric emulsifier in the resulting latex, whereby the ionic characteristic is inverted, is known in the prior art. The cationic nature of the latex prepared by the process is greatly reduced because a non-cationic emulsifier is included in the latex, and the adhesion of the latex to aggregates, its tackiness and rapid demulsifying properties are disadvantageously inferior to conventional cationic emulsions.
A polychloroprene latex prepared by using a cationic emulsifier is also known. However, the known polychloroprene latex is a gel polymer (benzene-insoluble polymer) so that molten asphalt can not be swelled or dissolved and an improved effect will not result. A need exists therefore for a cationic latex asphalt which will overcome the disadvantages of the prior art and which will combine the advantages of a cationic asphalt emulsion and a latex.